Apparatus for regulating the composition of a mixture of air and fuel-gas



July 11, 1961 R. P. scHRoPP 2,992,084

APPARATUS FOR REGULATINO THE COMPOSITION OF A MIXTURE OF AIR ANDFUEL-GAS Filed Aug. 1e, 195? IN VEN TOR.

00 oLF PHL/L SCA/@OPP M 2,992,084 APPARATUS 'FR REGULATING TI-m COMPOSI-TIN F A MXTURE 0F AIR AND FUEL-GAS Rudolf Paul Schropp, Maastricht,Netherlands, assigner to Le Four Industriel Belge, Uccle (Brussels),Belgium,

a corporation under Belgian laws Filed Aug. 16, 1957, Ser. No. 678,673Claims priority, application Belgium Aug. 2'4, 1956 4 Claims. ('Cl.48-180) The present invention relates to an apparatus for maintaining`constant the composition of a mixture of air and fuel-gas in adistribution piping in which one of the components of the mixture iscaused to enter a convergent nozzle with a narrowed extremity, to whichthe other component is conveyed, the two components then circulating ina divergent nozzle.

Apparatus of this type are known for regulating the composition of amixture of air and fuel-gas near the inlet of a gas burner or of aseries of burners, in which the gaseous uid at the highestpressure-generally the gasconveys the other gaseous Huid into a narrowedpart of a convergent-divergent nozzle, into which this other fluidpenetrates perpendicularly to the direction of ow of the iirst iluid. Inthis case, the latters kinetic energy is communicated to the othertiuid, resulting-from the afore- Vmentioned narrowed part onwardsin theproduction of a mixture of the two fluids. These apparatus suffer fromthe drawback of failing to ensure a constant proportion of air tofuel-gas in the mixture, under great variation in the delivery of themixture.

Attempts have also been made to produce a mixture of a constantcomposition, at the inlet of a burner or of a series of burners, byproviding regulating-devices for the individual delivery of each `of thecomponents which are operated in accordance with the total delivery.This dependence on the delivery of the mixture was brought about, forexample, by the pressure of the mixture, in such a way that theregulators opened wider when this pressure tended to decrease, as aresult of the coming into operation of a larger number of burners or ofan increase in the combustion-rate of the latter.

These already known apparatus are all subject to the drawback that thecomposition of the mixture varies with the counter-pressure at theoutlet from the burners.

The object oi the present invention is to provide an apparatus by whichthe composition of a mixture of fuelgas and air circulating in adistributing piping is kept constant, whatever pressure may prevail inthis piping upstream heating apparatus connected to it and whatevercounter-pressure may be present at the outlet from the latter.

The apparatus to which the invention relates is charactised in that aconvergent nozzle is prolonged in the form of a coaxial cylindricalpiping which is surrounded by a second piping which is substantiallycylindrical and is coaxial with the first and through which the secondcomponent of the mixture is conveyed into the diverging nozzle, in aparallel direction to the iirst of these components and at the samespeed, the divergent nozzle being so constructed that the maximumopening top angle must be 14 to 16 such that the speed of the twocomponents is converted into pressure without turbulence, in accordancewith Bernouillis law, and the second piping being fed from a chamberwhich surrounds the convergent nozzle and in which the second componentis kept at the same pressure as that which prevails in a chamber wherethe mixture is effected after leaving the divergent nozzle, by means ofa pressure-regulator in communication with this chamber.

Owing to the fact that the two uids circulate along coaxial paths, andat the same speed at 'the' place where 2,992,084 Patented July 11, 1961ICC they come in contact with each other, and the fact that they ow intothe divergent nozzle without turbulence, no kinetic energy iscommunicated from one to the other, and they do not substantially mixuntil after they have emerged from the divergent nozzle. l

The circulation of the second component of tlie mixture is brought aboutin the aforementioned second coaxial cylindrical piping as a result ofthe difference between the pressure in the chamber surrounding theconvergent nozzle and the pressure which is created around the outletfrom the first coaxial cylindrical piping and which is lower than thatcreated at the outlet from the divergent nozzle.

It is thus easy to determine the cross-section which has to be providedaround the outlet from the trst coaxial cylindrical piping to ensurethat the two fluids to be mixed together in accordance with a stipulatedratio shall move at the same speed within the plane of this outlet.

Experience has shown that when the pressure in the chamber surroundingthe convergent nozzle is equal to that in the mixing chamber, thecomposition of the mixture remains constant even if the pressure in thismixing chamber undergoes very great iluctuations and is reduced, forexample, to one eighth of the normal distribution pressure.

To obtain the desired constant ratio between the air and the gas, it issutl'lcient, since the tlow speeds of the `air and the gas are equal atthe outlet from the two coaxial cylindrical pipes in which these lluidscirculate, to ensure that the respective cross sections of these outletsbear the same proportion to each other as is desired for the two fluidsin the mixture.

When the apparatus is assembled, any minor errors which may be found inthe composition of the mixture may be corrected by an axial displacementof the coaxial pipe which forms an extension of the convergent nozzle,in the second coaxial pipe, provided that this latter has been given ashape slightly resembling that of a truncated cone. The cross section ofthe passage for the gaseous iluid, passing outside the other, at theinlet to the divergent nozzle, can thus be adjusted in such a way as toobtain the desired ratio.

A similar axial displacement can be carried out when the apparatus is inoperation, in order to make -a slight modification to the ratiooriginally selected.

According to an additional feature of the invention, the pipe whichestablishes communication between the pressure-regulator and themixing-chamber is connected to the air-supply pipe by means of a pipeequipped with a throttle.

This prevents any explosive mixture from iilling the chamber of thepressure-regulator, said chamber being inuenced by the pressure in themixing chamber.

This arrangement can be used to facilitate the ignition of the gases byenriching the mixture by installing a stop-valve on that part of thecommunicating pipe between the mixing chamber and the pressureregulator,k

which is situated between this chamber and the point where this pipecommunicates with the aforementioned throttle.

The invention will now be described with reference to the accompanyingdrawings which illustrate preferred embodiments by way of example and inwhich:

FIG. 1 is a schematic diagram, partly in section, of one embodiment ofthe invention, and

FIGS. 2 and 3 are sectional views of parts of two alternativeembodiments of the invention.

Throughout these drawings, the same reference numerals are used for thesame or similar parts.

The apparatus shown in lFIG. 1 comprises a pipe 2 for conveying one ofthe components of a mixture of air gaseosa and fuel-gas. Hereinafter,the said component is assumed to be air and the other component to befuel-gas, the latter being conveyed through a pipe 3.

A convergent nozzle is `secured to pipe 2 by means of a coupling l4, theshape of the nozzle being such that v'the air circulates through it inparallel jets. In other words, the ow of this air takes place inaccordance with Bernouillis law.

At -its outlet, the convergent nozzle 5 is extended in the form of asmall coaxial cylindrical pipe 6. This is surrounded by a second coaxialpipe '7 which is substantially cylindrical and which is in communicationwith a chamber 8 fed with gas by means of pipe 3 constituting an inletmeans therefor. This second coaxial pipe 7 has a shape slightlyresembling that of a truncated cone and has its outlet orifice near theplane of the outlet orifice of the cylindrical pipe 6, at the inlet of adiverging nozzle 9, which is also so constructed that the gaseous fluidscirculating therein follow Bernouillis law.

At the outlet from the diverging nozzle 9 there is a chamber 10, vwhichcommunicates with a pressure-regulator 11 by means of a pipe 12. Thispressure-regulator controls a pressure-reducer 13 with which pipe 3 isprovided, so that the gas-pressure in the chamber 8 yis equal yto thatprevailing in the chamber l0. The cross section of the passage providedfor `the gas around the outlet orifice of the iirst cylindrical pipe 6is such that the gas passes through it at the same speed as the airemerging from pipe 6.

Owing to the fact that the air and the gas are brought into contact witheach other in parallel jets and at the same speed and that they thencirculate in the aforementioned divergent nozzle 9, these two gaseousuids are not substantially mixed together until they have left thisnozzle.

The mixing of the fluids takes place in the chamber 10, and it is thepressure of the mixture that is established in the chamber 8, owing tothe pressure-regulator 11 and the pressure-reducer 13.

The coupling 4, the convergent nozzle 5 and the first coaxialcylindrical pipe 6 are made adjustable in their axial position so thatthe cross section of the passage offered to the gas can be accuratelyset to the air-gas ratio desired in the mixture. The coupling 4 issecured in position, for example, by means of screws 14, passing throughholes 15 in pipe 2.

The pipe 12 is connected to the air-supply pipe 2 by a pipe 16 equippedwith a throttle 17 controlled, for example by a needle-valve. Thisthrottle allows a slight Vcurrent of air to be conveyed to themixing-chamber 10, and a sufiicient quantity of this air passes throughpipe 12 to ensure that no explosive mixture is formed in the chamber ofthe pressure-regulator 11 above diaphragm 18 in the latter. If we assumethat the pipe 12 causes a negligible loss of pressure in the aircirculating therein, a pressure equal to that in the mixing chamber 10is easy to obtain, `downstream the throttle 17.

The pipe 12 is also equipped with a stop-valve 19. If this latter isclosed, the pressure established in the pressure-regulator 11 lis thesame as that prevailing in the air-pipe 2, and it is therefore possibleto increase the pressure in the chamber 8, whereby the gas-content ofthe mixture is enriched and ignition thereof facilitated.

In FIG. 2, the axial position of the coupling 4, the convergent nozzle 5and the iirst coaxial pipe 6 are regulated by screwing this coupl'mginto a pipe 20 which is in communication with pipe 2, the pipe 20 havinga cover l21 which is temporarily removed to enable the said adjustmentto be made.

In FIG. 3, the position of the coupling 4, the convergent nozzle 5 andthe iirst coaxial pipe 6 can be adjusted owing to the presence, on thesaid coupling, of two oppositelyformed screw-threads one of which servesfor engaging the air pipe 2 and the other engaging a socket 22 which isintegral with the divergent nozzle 9.

The invention is obviously not limited to the constructional examplesshown, and many modifications can be made to the shape, layout andcomposition of certain parts of the structure without departing from thescope of the appendant claims.

What I claim is:

l. An apparatus for maintaining constant the composition of a mixture ofair and fuel-gas in a distribution piping, comprising a convergentnozzle, means for feeding this convergent nozzle with one of the twoconstituents of the mixture, a cylindrical pipe coaxial with saidconvergent nozzle extending at the outlet of the latter, substantiallycylindrical pipe means surrounding the pipe coaxially with the latter, achamber with inlet means surrounding the convergent nozzle for feedingsaid pipe means with the other of the constituents of the mixture,divergent nozzle means into which the two constituents of the mixtureare delivered and connected to the outlet orifice of said pipe means,said cylindrical pipe extending to a point near said outlet orifice,said divergent nozzle means having the same axis as said convergentnozzle and having a maximum top opening angle of 16, a mixing chamber atthe outlet of the divergent nozzle means and pressure-regulator meanscommunicating with said mixing chamber and with the inlet means ot saidchamber surrounding the convergent nozzle and maintaining in this lastchamber the same pressure as that prevailing in the mixing chamber, saidpipe means coacting With the pressure maintained in the chambersurrounding the convergent nozzle to maintain equal the speeds of thetwo-constituents in the plane of the outlet of the pipe.

2. An apparatus for maintaining constant the com position of a mixtureof air and fuel-gas in a distribution piping, comprising a convergentnozzle, means for feeding this convergent nozzle with one of the twoconstituents of the mixture, -a cylindrical pipe coaxial with saidconvergent nozzle extending at the outlet of the latter, pipe meansslightly truncated surrounding the pipe coaxially with the latter, meansfor axially adjusting the position of said convergent nozzle and saidpipe, a chamber with inlet means surrounding the convergent nozzle forfeeding said pipe means with the other of the constituents of themixture, divergent nozzle means into which the two constituents of themixture are delivered and connected to the outlet orifice of said pipemeans, said cylindrical pipe extending to a point near said outletorifice, said divergent nozzle means having the same axis as the saidconvergent nozzle and having a maximum top opening angle of 16, a mixingchamber at the outlet of the divergent nozzle means, andpressure-regulator means communicating with said mixing chamber and withthe inlet means of said chamber surrounding the convergent nozzle andmaintaining in this last chamber the same pressure as that prevailing inthe mixing chamber, said pipe means coacting with the chambersurrounding the convergent nozzle to maintain equal the Speeds of thetwo constituents in the plane of the outlet of the pipe.

3. An apparatus for maintaining constant the composition of a mixture ofair and fuel-gas in the distribution piping, comprising a convergentnozzle, means for feeding this convergent nozzle with air, a cylindricalpipe coaxial with said convergent nozzle extending at the outlet of thelatter, substantially cylindrical pipe means surrounding the pipecoaxially with the latter, a chamber with inlet means surrounding theconvergent nozzle for feeding said pipe means with fuel-gas, a divergentnozzle means into which the two constituents of the mixture aredelivered and connected to the outlet orifice of said pipe means, saidcylindrical pipe extending to a point near said outlet orifice, saiddivergent nozzle means having the same axis as said convergent nozzleand .having a maximum top opening angle of 16, a mixing chamber at theoutlet of the divergent nozzle means, pressure-regulator meanscommunicating with said mixing chamber and with the inlet means of saidchamber surrounding the convergent nozzle and maintaining in this lastchamber the same pressure as that prevailing in the mixing charnber,said pipe means coacting with the pressure maintained in the chambersurrounding to the convergent nozzle to maintain equal the speeds of thetwo-constituents in the plane of the outlet of the pipe, a second pipecommunicating with the air feeding means of the convergent nozzle andwith a part `between said pressureregulator means and said mixingchamber, and a throttle in this last pipe.

4. An apparatus for maintaining constant the composition of a mixture ofair and fuel-gas in a distribution piping, comprising a convergentnozzle, means for feeding this convergent nozzle with air, a cylindricalpipe coaxial With said convergent nozzle extending at the outlet of thelatter, substantially cylindrical pipe means surrounding the pipecoaxially with the latter, a chamber with inlet means surrounding theconvergent nozzle for feeding said pipe means with fuel-gas, divergentnozzle means into which the two constituents of the mixture aredelivered and connected to the outlet orifice of said pipe means, saidcylindrical pipe extending to a point near said outlet orice, saiddivergent nozzle means having the same axis as said convergent nozzleand having a maximum top opening angle of 16, a mixing chamber at theoutlet of the divergent nozzle means, pressure-regulator meanscommunicating with said mixing chamber and with the inlet means of saidchamber surrounding the convergent nozzle and maintaining in this lastcharnber the same pressure as that prevailing in the mixing chamber,said pipe means coacting with the pressure maintained in the chambersurrounding the convergent nozzle to maintain equal the speeds of thetwo-constituents in the plane of the outlet of the pipe, a second pipecommunicating with the air feeding means of the convergent nozzle andwith a part between said pressure-regulator means and said mixingchamber, a throttle in this last pipe, and a stop-valve between saidmixing chamber and the part where the pipe provided with said throttleis in communication with the pressure-regulator means.

References Cited in the file of this patent UNITED STATES PATENTS1,519,649 Anderson Dec. 16, 1924 2,155,754 Ensign Apr. 25, 19392,342,426 Ransome Feb. 22, 1944 2,366,322 Foster Ian. 2, 1945

1. AN APPARATUS FOR MAINTAINING CONSTANT THE COMPOSITION OF A MIXTURE OFAIR AND FUEL-GAS IN A DISTRIBUTION PIPING, COMPRISING A CONVERGENTNOZZLE, MEANS FOR FEEDING THIS CONVERGENT NOZZLE WITH ONE OF THE TWOCONSTITUENTS OF THE MIXTURE, A CYLINDRICAL PIPE COAXIAL WITH SAIDCONVERGENT NOZZLE EXTENDING AT THE OUTLET OF THE LATTER, SUBSTANTIALLYCYLINDRICAL PIPE MEANS SURROUNDING THE PIPE COAXIALLY WITH THE LATTER, ACHAMBER WITH INLET MEANS SURROUNDING THE CONVERGENT NOZZLE FOR FEEDINGSAID PIPE MEANS WITH THE OTHER OF THE CONSTITUENTS OF THE MIXTURE,DIVERGENT NOZZLE MEANS INTO WHICH THE TWO CONSTITUENTS OF THE MIXTUREARE DELIVERED AND CONNECTED TO THE OUTLET ORIFICE OF SAID PIPE MEANS,SAID CYLINDRICAL PIPE EXTENDING TO A POINT NEAR SAID OUTLET ORIFICE,SAID DIVERGENT NOZZLE MEANS HAVING THE SAME AXIS AS SAID CONVERGENTNOZZLE AND HAVING A MAXIMUM TOP OPENING ANGLE OF 16*, A MIXING CHAMBERAT THE OUTLET OF THE DIVERGENT NOZZLE MEANS AND PRESSURE-REGULATOR MEANSCOMMUNICATING WITH SAID MIXING CHAMBER AND WITH THE INLET MEANS OF SAIDCHAMBER SURROUNDING THE CONVERGENT NOZZLE AND MAINTAINING IN THIS LASTCHAMBER THE SAME PRESSURE AS THAT PREVAILING IN THE MIXING CHAMBER, SAIDPIPE MEANS COACTING WITH THE PRESSURE MAINTAINED IN THE CHAMBERSURROUNDING THE CONVERGENT NOZZLE TO MAINTAIN EQUAL THE SPEEDS OF THETWO-CONSTITUENTS IN THE PLANE OF THE OUTLET OF THE PIPE.